Transonic region a problem.

[Screeno]

Ok so, I'm having a problem with flying rapier ssto's in the transonic region, as the rapier struggles massively to go from just under mach 1 to supersonic, like, my ssto (a Mk 2 fuselage based ssto, 45 tons with four rapiers and 2 nukes just to clarify) which im flying now will accelerate fine from takeoff at a 30 degree angle, but when it gets closer to supersonic the thrust of the rapiers drops, the speed drops, even using the nukes to help it break through to mach 1 does nothing. i actually have to dive if i want to break the sound barrier, like 20 degrees below! then pitching up to get back to climbing again i loose speed and go back to below 300m/s even...

either im doing this all wrong or 1.2.0 aero has way to much drag in the transonic region...

also if anyone could post the old 1.0 aero config that would be great. i think id be better off making a config exactly between 1.0 and 1.2.0

even though i do not like modding ksp at all.. i like to keep it stock.. just feels like cheating to me but now for the sake of my own fun i need too...

[AviatOrme]

What altitude are we talking here? If you climb into thinner air, you should find it far easier to speed up as the drag decreases. If you want to go supersonic at sea level, you need to think a lot more about the TWR of the aircraft and how many draggy bits you have sticking off the side.

[Screeno]

well, ill try climbing steeper and waiting longer to start my turn you mean?

[Red Iron Crown]

The bump in drag at Mach 1 is pretty steep in 1.0.2. I've been finding it better to do a subsonic climb up to 10-12km altitude before leveling off and punching through the sound barrier. Too much engine is needed for supersonic flight at lower altitudes.

[cybersol]

With 4 rapiers and only 45 total tons, you should be able to go to 5* upslope at 12-15 km altitude and punch through the transonic barrier. Otherwise, you may have too much drag in you design. If that is the case, maybe you could post a screenshots showing the design and another with drag lines on while going 300 m/s.

[Screeno]

I still get the same problem, my craft can't climb fast enough, like, ill get 50/ms on a 45 degree climb, and when I want to gain speed ill still have to pitch down well below horizon. Im gonna have to change my config, the transonic drag is retarded. That's the only thing wrong with 1.2.0 . Does anyone have the old 1.0 config so I can look at both and put it in the middle?

here are the pictures

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Edited May 12, 2015 by Screeno

[Red Iron Crown]

Screeno, those draggy shuttle wings are the trouble I think, a plane in that weight class doesn't need nearly so much wing, I made a similarly sized one with just two pairs of delta wings plus some control surfaces and it had enough lift, could climb at 45 degrees and steadily accelerate, and went supersonic fairly easily at about 12km altitude.

The test payload of ore is about equivalent in mass to the two LV-Ns and crew tank in your design.

[Screeno]

How much fuel did you have and how much was left when you got into orbit?

The thing is I needed the shuttle wings because they contain liquidfuel which I seem to need about 800 units in orbit (which the two big s wings and wing strakes give exactly) to rendezvous with my space station (75x75 km equatorial orbit) it always did that in 1.0 the oxidizer is all consumed when the rapiers go to rocket mode to push the apoapsis to 75 km. I just wonder where I could put more liquidfuel without causing more drag or messing with the com/ col balance (currlently its balanced dry and wet)

Edited May 12, 2015 by Screeno

[Red Iron Crown]

On the runway it had 1815 units of LF and 1485 units of O. After insertion into a 75x75km orbit it had about 190m/s of dV plus about 100 extra units of LF, enough to deorbit and do some flying in atmo.

Honestly, if you're using it to ferry crew back and forth from LKO the nukes are probably unnecessary. You'd likely be better served by replacing them with an equivalent mass of LFO tankage and using the RAPIERs for orbital maneuvers. Or you could reduce the size of the whole thing like so:

This one gets to 75x75km orbit with about 500m/s of dV remaining, enough for a rendezvous if done carefully.

If you insist on keeping the LV-Ns (perhaps you plan to take it further than LKO), you could add another liquid fuel fuselage to the front of your RAPIER stacks, or alternately replace the intercoolers with LF tanks.

Funny timing, I just built these planes over the last few days and they seem to match the roles of yours almost perfectly.

[match]

I've been messing around with ssto lately and using the F12 debug for aerodynamics. It seems to me that having too little lift has quite an impact, especially in the transonic region. As the AoA grows, those drag markers get really big (I am assuming that is bad).

I've been erring toward more lift rather than just enough with better success in the transition.

[Screeno]

Cool coincedence Mr red crown and yes I plan to take it beyond my stations orbit, testing if it can make it to the mun and minimus and back and stuff, then seeing if it could make the round trip to duna... But maybe it would just be landing on ike as nervas would produce less thrust on duna because of the atmo, but to counteract this I could just refuel some oxidiser for a. Little rapier boostt basically I'm manufacturing an ssto that could become an interplanetary ship, once refueled either at LKO, or minimus orbit, (i don't know which is better for delta v in a transfer?) to the surface of duna, ike, fully (definatley not eve lol) probably dres, possibly moho, but I don't think so, and I am sure it couldn't make it to the joolian system or further though.

[Geschosskopf]

Screeno, those draggy shuttle wings are the trouble I think, a plane in that weight class doesn't need nearly so much wing, I made a similarly sized one with just two pairs of delta wings plus some control surfaces and it had enough lift, could climb at 45 degrees and steadily accelerate, and went supersonic fairly easily at about 12km altitude.

Ah, the shuttle wings. I've been trying to decide whether to use them or not. The SSTO in question is for crew rotations at the Laythe colony. Laythe doesn't have a runway so the plane needs good short-field performance. Short takeoffs can be achieved with sufficient thrust but short landings need low stall speeds, which means a reasonably large wing area. Large wings make large drag. Thus, the need to minimize drag elsewhere.

So here's the thing. The shuttle wings can hold fuel, which reduces the need for separate tankage elsewhere, either in terms of a longer, less off-road-friendly fuselage or in drag-infested radial tankage. But the shuttle wings are drag-infested themselves. NOTE: the spaceplane needs some radial tankage anyway because it's twin-RAPIER and I need the rear of the fuselage for the transfer tug's docking port. Thus, the question: for this particular application, does the drag saved by using the wing tankage compensate for using the shuttle wings in the 1st place, keeping in mind that a fairly short, slow-landing plane is desired?

I have finally managed to build a shuttle-winged Laythe SSTO that works. On Kerbin, it will ROG by itself at 60m/s, can land at 35m/s, and stop on a dime. I expect slightly higher speeds will be required on Laythe due to thinner air, but not that much difference based on previous experience. Still, that should be fine for off-road operations. Anyway, the plane is incapable of going supersonic in level flight, so I climb to 16km, dive at -15^ to about 12km, level at 10km, then away I go. Seems horribly inefficient. Any thoughts for improvement?

[Screeno]

Also I had a weak moment... I felt bad at first, but..I changed the Physics Cfg... Not to 1.0 settings, that would be a bit too much, but I put the settings exactly between the ones from 1.0 and 1.2.0. And it works like a dream! fun is back for me for now haha, My ssto went to orbit with 800 something LF remaining just docking with my station now. And then I will refuel, and test its real power! To minimus first. After it gets back, I'm sure it will Then if it performs well there ill launch another and try for the mun

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(personnaly I think squad should pat h the game to be inbetween 1.0 configs and 1.2.0 that would please people suficenlty I thnik )

[Red Iron Crown]

Ah, the shuttle wings. I've been trying to decide whether to use them or not. The SSTO in question is for crew rotations at the Laythe colony. Laythe doesn't have a runway so the plane needs good short-field performance. Short takeoffs can be achieved with sufficient thrust but short landings need low stall speeds, which means a reasonably large wing area. Large wings make large drag. Thus, the need to minimize drag elsewhere.

I would be tempted to touch down at higher speed and use airbrakes to bleed off speed quickly if trying for a short landing roll. You could also try using control surfaces as flaps for added lift when deployed, then retracting them to reduce drag.

So here's the thing. The shuttle wings can hold fuel, which reduces the need for separate tankage elsewhere, either in terms of a longer, less off-road-friendly fuselage or in drag-infested radial tankage. But the shuttle wings are drag-infested themselves. NOTE: the spaceplane needs some radial tankage anyway because it's twin-RAPIER and I need the rear of the fuselage for the transfer tug's docking port. Thus, the question: for this particular application, does the drag saved by using the wing tankage compensate for using the shuttle wings in the 1st place, keeping in mind that a fairly short, slow-landing plane is desired?

I suspect that a design that can get by with two RAPIERs does not need all that wing area.

Drag-wise, I try to minimize the fuselage cross-section as much as possible; generally this means cross-section is determined by the number of engines required. I will only add radial tanks when more engine is needed, and I would not use precious rear cross-section area for non-engine parts like docking ports if at all avoidable. I haven't seen your design, is it feasible to mount the docking port for the tug in the nose?

Keeping it short is less of a benefit than it might seem. If you are concerned about tailstrikes when landing you can just add another pair of gear near the rear that are only used when landing, retract them manually before takeoff for pivoting.

I have finally managed to build a shuttle-winged Laythe SSTO that works. On Kerbin, it will ROG by itself at 60m/s, can land at 35m/s, and stop on a dime. I expect slightly higher speeds will be required on Laythe due to thinner air, but not that much difference based on previous experience. Still, that should be fine for off-road operations. Anyway, the plane is incapable of going supersonic in level flight, so I climb to 16km, dive at -15^ to about 12km, level at 10km, then away I go. Seems horribly inefficient. Any thoughts for improvement?

RAPIERs can be tricky that way, sometimes you need to do odd things to get them into the sweet spot of their thrust curves. Nothing wrong with descending a bit to build up speed to get them going; I've tried some designs that require it for the initial climb (otherwise the thrust falloff with increasing altitude would kill the ascent). Still, I think you'd be better served with less wing/drag. You might find that not only does it accelerate better, but it also consumes less fuel during the initial ascent due to the lower drag.

Disclaimer: Take all the above with a grain of salt, I am far from a plane expert compared to some others around here. I've just been messing around with them a lot since 1.0 came out.

[Geschosskopf]

Also I had a weak moment... I felt bad at first, but..I changed the Physics Cfg... Not to 1.0 settings, that would be a bit too much, but I put the settings exactly between the ones from 1.0 and 1.2.0. And it works like a dream! fun is back for me for now haha....

Bravo! Sounds like a good idea. KSP should be about impossible dreams coming true, not having them crushed by harsh reality. +1.

PS, mind sharing your tweaks? I have no idea what 1.0 was so have no reference where halfway between that and 1.0.2 .

[Screeno]

not having them crushed by harsh reality.

you mean, getting crushed by too much drag in the transonic region XD oh yeah ill find them for you just give me a minute ill get em

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Here you are Geschosskopf

dragMultiplier = 7.0

dragCubeMultiplier = 0.08

angularDragMultiplier = 2

liftMultiplier = 0.045

liftDragMultiplier = 0.027

bodyLiftMultiplier = 9

[Geschosskopf]

Thanks

[n0xiety]

This is a quick ascent spaceplane that doesn't care about fuel much. I made it so when you start climbing with 20 degrees it adjusts its own climbing degree as it goes up so you don't have to touch anything and micromanage and it reaches 120km orbit in about 9 real life minutes. This one can carry 2 tons easy, 3 tons if you push it. Tho you can always remove the clampotron and crew cabin modules and get 3 more tons of capacity making it go up to 6 tons.

I documented the whole flight and you can see the fuel levels too. Carrying a rapier engine which weighs 2tons. I would suggest using only 1 nuke since it allready is heavy enough. And as you can see 1 nuke is more than enough at vacuum stage. This is by no means the most efficient craft there is. I don't even care about fuel since i like it that way and go %100 throttle from get go. I just hate micromanaging and slow ascent but thats just me.

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